The present invention relates to a variable mirror capable of varying the configuration of a reflecting mirror to change the reflecting direction of light.
Another invention in the present invention relates to an optical apparatus including a variable-optical-characteristic optical element, a variable-optical-characteristic mirror, or a combination thereof.
Still another invention in the present invention relates to an optical system using the above-described variable mirror, etc. More particularly, the invention relates to an optical system capable of focusing, etc. for a camera, a video camera, a digital camera, a finder, a viewing optical system, an image display device, and so forth.
This type of variable mirror is widely known, for example, from Japanese Patent Application Unexamined Publication (KOKAI) No. 5-157903. A variable mirror described in this publication is produced in a very small size by making use of a semiconductor manufacturing technique with a view to using the variable mirror in a micromachine. The variable mirror has a mirror body formed from a sheet 1 of single crystal silicon. As shown in part (A) of FIG. 80, the sheet 1 includes a thin inner portion 11 and a thick outer peripheral frame portion 12 surrounding the inner portion 11. The sheet 1 is supported at the outer peripheral frame portion 12 by a thick outer peripheral frame portion 13a of a glass substrate 13, which is a support member. The glass substrate 13 has a thin inner portion 13b surrounded by the outer peripheral frame portion 13a. A space is created between the inner portion 13b of the glass substrate 13 and the inner portion 11 of the sheet 1. An electrode film 13c is formed on the upper surface of the inner portion 13b of the glass substrate 13.
An upper surface 11a of the inner portion 11 of the sheet 1 is a flat mirror-finished surface, and a lower surface 11b thereof is a flat finished surface, although it is not a mirror surface.
In the conventional variable mirror arranged as stated above, when a voltage is applied between the sheet 1 and the electrode film 13c, electrostatic attraction occurs therebetween, causing the inner portion 11 of the sheet 1 to curve so as to be convex toward the electrode film 13c. Consequently, the upper surface 11a forms a concave mirror. The degree of curvature of the inner portion 11 can be changed according to the magnitude of the above-described voltage. Accordingly, by changing the magnitude of the voltage, the position of the focus F of the concave mirror, which is formed by the upper surface 11a, can be moved along an optical axis 0 of the concave mirror.
However, the conventional variable mirror, in which the inner portion 11 is formed with a uniform thickness as stated above, suffers from the problem that the curved inner portion 11 is a biquadratic surface and therefore the concave mirror of the upper surface 11a produces unfavorably large aberrations.
To solve the problem, Japanese Patent Application Unexamined Publication (KOKAI) No. 5-157903 proposes an arrangement such as that shown in part (B) of FIG. 80. In this arrangement, the lower surface 11bxe2x80x2 of the inner portion 11 of the sheet 1 is not flat but formed from a plurality of curved surfaces. More specifically, the lower surface 11bxe2x80x2 is constructed by forming different curved surfaces concentrically. The central portion of the lower surface 11bxe2x80x2 is formed from a paraboloid A. A peripheral portion surrounding the central portion of the lower surface 11bxe2x80x2 is formed from a cubic surface B. Because the lower surface 11bxe2x80x2 is formed by combining together a plurality of curved surfaces, when the inner portion 11 is curved by electrostatic attraction as stated above, the upper surface 11a becomes a concave mirror formed from a paraboloid (quadratic surface). Accordingly, large aberrations are not produced.
The configuration of the lower surface 11bxe2x80x2 shown in part (B) of FIG. 80 is determined by a mathematical expression. The lower surface 11bxe2x80x2 is formed by laser-assisted etching. However, as the external size of the variable mirror decreases, it becomes more difficult to form the lower surface 11bxe2x80x2 into such a complicated configuration with high accuracy [particularly within xcex (wavelength of light)/n (n is generally a value of about 10), which is optical tolerances required]. In addition, it is desired to allow the mirror surface to be changed into even more various configurations other than the paraboloid (quadratic surface), as desired, so that the mirror surface can be applied to various optical systems.
Moreover, large electric power is needed to increase the degree of curvature of the inner portion 11 in the above-described conventional variable mirror, in which the inner portion 11 of the sheet 1 is curved so as to be convex toward the electrode film 13c by utilizing electrostatic attraction, thereby forming the upper surface 11a into a concave mirror.
Conventionally, a digital camera is built by assembling together components as shown in FIG. 81, i.e. a plastic lens PL, a diaphragm D, a focusing solenoid FS, a shutter S, a charge-coupled solid-state image pickup device (CCD), a signal processing circuit PC, and a memory M.
Incidentally, the image-forming performance of plastic lenses generally degrades with changes in temperature because the refractive index and configuration thereof change with changes in temperature and humidity. Therefore, glass lenses are mostly used. For this reason, there are limits to the achievement of a reduction in weight, increase in accuracy and reduction in cost of products.
There has heretofore been known a prism optical system formed by combining a free-form surface and a prism with an optical system of a digital camera or the like as disclosed, for example, in Japanese Patent Application Unexamined Publication (KOKAI) Nos. 9-211330 and 9-211331. In these prior art references, however, no mention is made of a method of focusing for each object position.
Focusing of such a prism optical system is mentioned in part in Japanese Patent Application Unexamined Publication (KOKAI) No. 10-68886. However, what is mentioned therein is a focusing mechanism in which focusing is performed by moving a prism or an image plane along an optical axis as in the case of a coaxial system.
Meanwhile, there has heretofore been an adaptive optics technique in which the disturbance of the wavefront caused by atmospheric fluctuation is corrected by inserting a variable mirror in an optical system of a telescope [e.g. xe2x80x9cApplied Physicsxe2x80x9d, Vol. 61, No. 6 (1992), pp. 608-611].
Regarding a focusing system for focusing or diopter adjustment in a reflecting optical system using a rotationally asymmetric surface, because the optical system is a decentered optical system using a rotationally asymmetric surface, if focusing is effected with a lens frame-rotating mechanism similar to that used for a coaxial system, when the rotationally asymmetric optical system rotates together with the lens frame, the image also rotates undesirably. To prevent this, it is necessary to change the distance to the image plane without rotating the rotationally asymmetric optical system. The scheme for preventing the rotation of the image causes the number of components to increase and results in an increase in size of the apparatus, unfavorably.
In the case of aiming principally at mass-production of the decentered reflecting optical system using a rotationally asymmetric surface, it is common practice to employ a technique of production by molding. In the production by molding, however, significant errors are introduced into optical parts produced, causing the optical performance to be degraded.
Although the following matter is not limitative to the decentered reflecting optical system using a rotationally asymmetric surface, the refractive index and configuration of optical parts generally change according to environmental conditions, e.g. temperature and humidity, causing the optical performance to be degraded.
In a zoom optical system, it is impossible to actively change the condition of aberration that varies with the change of the zoomed condition.
In view of the above-described problems with the prior art, an object of the present invention is to provide a variable mirror that is readily formable so that even when the external size thereof decreases, the variable mirror can be readily changed into various configurations as desired.
Another object of the present invention is to provide a variable mirror capable of obtaining a desired degree of curvature with small electric power even when it is produced with such a small external size that the variable mirror can be used in a micromachine.
Still another object of the present invention is to provide various optical apparatus capable of compensating for a change in image-forming performance or various other optical performance caused by a change in temperature or humidity, e.g. a digital camera, a video endoscope, a portable data terminal (PDA), a video telephone, a VTR camera, a television camera, a film camera, a microscope, a laser scanning microscope, a bar code scanner, a bar code reader, and a pick-up for optical discs.
A further object of the present invention is to provide, in a decentered reflecting optical system using a rotationally asymmetric surface, a compact and readily implementable focusing system for focusing or diopter adjustment, a system for reducing optical performance degradation caused by manufacturing errors or changes in environmental conditions, e.g. temperature and humidity, a system for correcting aberration associated with zooming, and a hand-shake correcting system.
To attain the above-described first object of the present invention, a variable mirror according to a first invention in the present invention is a variable mirror having a mirror body formed of an elastic or flexible material and having one surface functioning as a reflecting surface. The mirror body is capable of changing the reflecting surface configuration. The variable mirror is characterized in that the rigidity of the mirror body varies in a direction parallel to the one surface.
A desired curved surface configuration of the reflecting surface configuration of the mirror body is determined by the set of curvatures at arbitrary points on the reflecting surface configuration. The curvature at each arbitrary point is determined by a combination of a load applied to the arbitrary point and the rigidity.
Therefore, the above-described variable mirror according to the first invention is a variable mirror having a mirror body formed of an elastic or flexible material and having one surface functioning as a reflecting surface. The mirror body is capable of changing the reflecting surface configuration. The rigidity of the mirror body is varied in a direction parallel to the one surface, thereby allowing the reflecting surface configuration of the mirror body to be readily changed to a desired curved surface configuration. The mirror body itself is also readily formable. The variation in rigidity need not be continuous as in the variation in thickness in the above-described prior art but may be varied stepwisely at arbitrary points. Therefore, formation of the mirror body is facilitated.
To attain the above-described object of the first invention, the variable mirror according to the invention may be arranged such that the other surface of the mirror body, which is reverse to the one surface, is formed from a plurality of flat portions of different thicknesses, whereby the rigidity of the mirror body varies in a direction parallel to the one surface.
A difference in thickness produces a difference in rigidity, and a difference in area also produces a difference in rigidity. Accordingly, by forming the other surface, which is reverse to the one surface, from a plurality of flat portions of different thicknesses (i.e. portions different in rigidity from each other), the reflecting surface configuration of the mirror body can be readily changed to a desired curved surface configuration, and the mirror body itself can also be readily formed. The variation in thickness or the variation in area (i.e. the variation in rigidity) need not be continuous as in the variation in thickness in the above-described prior art but may be varied stepwisely at arbitrary points. Therefore, formation of the mirror body is facilitated. Thus, in the case of varying the thickness also, a difference in rigidity can be produced by making the portions of the same thickness vary in area from each other.
To attain the above-described object of the first invention, the variable mirror according to the invention may be arranged such that the material of the mirror body varies in a direction parallel to the one surface thereof, whereby the rigidity of the mirror body varies in a direction parallel to the one surface.
A difference in material produces a difference in rigidity. Accordingly, by varying the material of the mirror body (i.e. the rigidity thereof) in a direction parallel to the one surface as stated above, the reflecting surface configuration of the mirror body can be readily changed to a desired curved surface configuration, and the mirror body itself can also be readily formed. The variation in material (i.e. the variation in rigidity) need not be continuous as in the variation in thickness in the above-described prior art but may be varied stepwisely at arbitrary points. Therefore, formation of the mirror body is facilitated. Thus, in the case of varying the material also, a difference in rigidity can be produced by making the portions of the same material vary in area from each other.
To attain the above-described second object of this invention, a variable mirror according to a second invention in the present invention is a variable mirror capable of changing the configuration of a reflecting surface. The variable mirror is characterized by including: a mirror body having a light-reflecting surface for reflecting light; a support member for supporting a part of the mirror body; and a driving force transmitting means provided to project from the mirror body so as to transmit input driving force for changing the configuration of the reflecting surface to the mirror body.
In the variable mirror according to the second invention, which is characterized by being arranged as stated above, the driving force transmitting means is capable of increasing even such small driving force as electrostatic attraction by accumulating it. The magnitude of driving force to be accumulated can be freely preset independently of the size of the mirror body. A place where the driving force increased as stated above is made to act on the mirror body can be determined to be any desired place irrespective of the external shape of the mirror body. Even when the variable mirror according to the second invention is produced with such a small external size that the variable mirror can be used in a micromachine, a desired degree of curvature can be readily obtained with small electric power.
In the variable mirror according to the second invention, which is characterized by being arranged as stated above, it is preferable for the driving force transmitting means to have a driving force receiving member extending along the reflecting surface of the mirror body at a position away from the mirror body on a side thereof reverse to the reflecting surface so that the above-described driving force is input to the driving force receiving member.
Such a driving force receiving member can be prepared easily, and the magnitude of driving force to be accumulated in the driving force transmitting means can be readily set at will by changing the plane area of the driving force receiving member.
In the variable mirror according to the second invention, which is characterized by being arranged as stated above, it is preferable that the side of the mirror body that is reverse to the reflecting surface be formed with grooves in a predetermined pattern for changing the reflecting surface of the mirror body into a desired configuration when the driving force is transmitted to the mirror body by the driving force transmitting means.
Such grooves can be prepared easily. Accordingly, it is possible to readily set the arrangement so that when the driving force is transmitted to the mirror body by the driving force transmitting means, the reflecting surface of the mirror body can be changed into a desired configuration. The predetermined pattern includes the size, shape and overall arrangement of grooves.
To attain the above-described third object, an optical apparatus according to a third invention in the present invention comprises a variable-optical-characteristic optical element.
The optical apparatus according to the third invention also comprises a variable-optical-characteristic mirror.
According to the third invention, the variable-optical-characteristic mirror comprises a combination of a variable-optical-characteristic lens and a mirror.
A decentered optical system according to a fourth invention in the present invention, which is provided to attain the above-described fourth object of the present invention, is a decentered optical system having at least one reflecting surface with a rotationally asymmetric surface configuration. The decentered optical system is characterized by including an active reflecting optical element capable of changing the direction of reflection for each position in the reflecting surface.
In this case, it is desirable for the active reflecting optical element to constitute at least one reflecting surface of the decentered optical system.
Examples of active reflecting optical elements include a variable-configuration mirror capable of changing the surface configuration and a variable-refractive-index mirror capable of freely changing the refractive index of an optical medium adjacent to the entrance side of the reflecting surface.
It is desirable that the mirror surface of the active reflecting optical element have a rotationally asymmetric surface configuration for correcting rotationally asymmetric aberrations produced by the mirror surface. The mirror surface of the active reflecting optical element may have a rotationally symmetric surface configuration. However, it is preferable from the viewpoint of aberration correction that the mirror surface have a rotationally asymmetric surface configuration for the purpose of correcting rotationally asymmetric aberrations produced by the mirror surface because the entrance rays are in decentered positional relation to the mirror.
Because the fourth invention includes an active reflecting optical element capable of changing the direction of reflection for each position in the reflecting surface, it is possible to perform, with a simple arrangement, focus adjustment and diopter adjustment of a decentered reflecting optical system, correction of aberration variations caused by zooming, compensation for variations in optical performance caused by changes in temperature and humidity, compensation for manufacturing errors of optical elements, hand-shake correction, etc.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.